The primary objective is to synthesize radioiodinated fatty acids suitable for myocardial imaging. Various classes of straight chain fatty acids, saturated, monounsaturated and polyunsaturated, will be synthesized, radioexchange labeled and evaluated in animals. Chain modified fatty acids (modifications proposed include methyl, dimethyl, dimethyl, cyclopropyl and dicarboxyl) and carboxylate modified fatty acids will also be synthesized and evaluated in animals. Fatty acid syntheses are outlined and are designed to provide a series of compounds by utilizing a general method with reactants of varying lengths. Animal evaluation will consist of tissue distribution studies in rats and dogs and imaging studies with promising fatty acids in dogs with and without myocardial infarctions. Fatty acids designed to behave as mechanism-based irreversible inhibitors will also be evaluated biochemically to determine if such inhibition was achieved. A determination will be made as to whether or not the iodinated fatty acids are substrates for the known deiodinases.